不同粒度纳米碳酸钙的可控制备

不同粒度的纳米碳酸钙具有不同的特性和应用范围,目前不同粒度纳米碳酸钙的可控制备方法还未见报道。以氯化钙、碳酸铵为原料,以乙醇、柠檬酸和焦磷酸钠为分散剂,采用复分解法研究了不同制备条件对纳米碳酸钙粒径的影响规律,在此基础上制备出平均粒径为17~71 nm的碳酸钙,并对其进行了表征。实验结果表明,所制备的纳米碳酸钙均为球霰石型,纯度很高,而且形貌近似球形。制备条件对纳米碳酸钙的粒径有显著的影响：随着反应温度升高,纳米碳酸钙的粒径减小;随着氯化钙滴加时间的增加,纳米碳酸钙的粒径增大;随着反应物浓度的提高,纳米碳酸钙的粒径先减小后增大;当分散剂为柠檬酸和焦磷酸钠的混合溶液时所得纳米碳酸钙的粒径最小,当分散剂为乙醇和焦磷酸钠的混合溶液时所得纳米碳酸钙的粒径最大。利用这些影响规律通过控制制备条件可以实现所需粒径纳米碳酸钙的可控制备。     

分散剂对柠檬酸络合法制备氧化镧钇亚微米粉体的影响

以硝酸镧、硝酸钇和柠檬酸为原料,采用柠檬酸络合法制备氧化镧钇亚微米粉体,分别探讨了PEG400和油酸作为分散剂时对粉体物相、微观形貌以及粒径分布的影响规律.结果发现,无论是以PEG400还是油酸作为分散剂,煅烧后获得的粉体中只存在Y2O3单相,且粉体粒径随着煅烧温度的升高而变大;PEG400的最佳添加量为4wt％,此时粉体在1100℃煅烧后的一次粒径D50在85 nm左右;油酸的最佳添加量为2wt％,此时粉体在1100℃煅烧后的一次粒径D50在75 nm左右;使用油酸作为分散剂明显比使用PEG400作为分散剂的团聚峰平缓,说明油酸的分散效果比PEG400的分散效果更为优异.     

纳米碳化硼在水基础液中的分散稳定性

以纳米碳化硼粉体为纳米材料,聚乙二醇、羧甲基纤维素钠为分散剂,蒙脱石为抗沉降稳定剂,RO反渗透膜处理水为分散介质,采用两步法制备了水基纳米碳化硼溶液.研究了不同分散条件对纳米碳化硼在水基础液中的分散情况,并采用沉降稳定性分析、流变特性分析来评价其分散效果.实验结果表明,分散剂种类、分散剂质量分数、纳米碳化硼的粒径、纳米碳化硼的质量分数都会对溶液分散稳定性产生一定的影响.研究得出,用质量分数为0.4%的聚乙二醇(PEG600)作为分散剂、用粒径为60nm的纳米碳化硼且质量分数为0.8%～0.9%时,能够使得纳米碳化硼在水基础液中达到最佳稳定分散的效果.     

羟基磷灰石基活性生物陶瓷的性能研究

采用共沉淀法制备羟基磷灰石,并在制备过程中引入PVA、无水乙醇和柠檬酸作分散剂,比较这3种分散剂的分散效果并探讨了最佳工艺参数。实验结果表明:使用0.2mol/L的Ca(NO_3)_2溶液为原料,以0.5mol/L无水乙醇作为分散剂制备的HAP粉体产物粒径最小;经过1100℃烧结的陶瓷样品强度最高;添加玻璃粉可增加陶瓷强度,并随着玻璃粉含量的增加,强度也增大;在HAP粉体中添加玻璃粉,使陶瓷的线收缩率、密度变小,同时可提高陶瓷的气孔率和耐酸性,其中骨灰陶瓷的气孔率和耐酸性最好。     

颗粒级配法制备高固相含量低黏度氧化铝料浆

以平均粒径分别为0.97 μm(CQ)和2.18 μm(HNXY)的2种Al2O3粉体为原料采用级配混合的方法,分别添加离子型分散剂柠檬酸铵或高聚物型分散剂聚丙烯酸,制备了适合胶态成型的高固相含量、低黏度的料浆.讨论了胶态成型中粒度分布,以及分散剂的种类和各自不同的用量对悬浮体流变学特性的影响.当粉体CQ和HNXY的级配质量比为1:2时,其混合粉体粒度分布最接近于Dinger模型理论分布,此时可以得到黏度最低的料浆,当固相含量为65%(体积分数)时,料浆的黏度仍然在1 Pa·s以下;与分散剂柠檬酸铵相比,在相同的周相含量和级配比例下,采用聚丙烯酸的科浆流动性更好.     

分散剂及复合介质对石蜡-聚苯乙烯微球合成的影响

通过悬浮聚合法合成石蜡-聚苯乙烯微球,研究了合成过程中复合介质的配比和用量以及分散剂种类和用量对微球粒径及其分布的影响。实验结果表明:采用聚乙烯醇作分散剂,更有利于合成小粒径、高产率的石蜡-聚苯乙烯微球,悬浮聚合体系中水-乙醇复合介质的最佳体积配比和用量分别为1:2.5和150mL。     

石蜡聚苯乙烯微球的制备Ⅱ.分散剂及复合介质的影响

通过悬浮聚合法合成了石蜡聚苯乙烯微球,研究了合成过程中复合介质的配比和用量以及分散剂种类和用量对微球粒径及其分布的影响。结果表明:采用聚乙烯醇作分散剂,更有利于合成小粒径高产率的石蜡聚苯乙烯微球,悬浮聚合体系中水-乙醇复合介质的最佳体积配比和用量分别为1:2.5和150mL。     

分散剂对水热法合成镍钴铁氧体结构和吸波性能的影响

在水热法合成镍钴铁氧体的过程中分别加入不同分散剂[柠檬酸、十六烷基三甲基溴化铵(CTMAB)、十二烷基苯磺酸钠(SDBS)、聚乙烯醇(PVA)、十二烷基磺酸钠(SDS)],借助于FTIR、XRD、SEM和网络矢量仪等现代测试技术研究分散剂对镍钴铁氧体结构和性能的影响。结果表明,柠檬酸不利于尖晶石镍钴铁氧体的生成。在水热合成过程中,分散剂的存在并未影响铁氧体的化学组成和物相结构。以SDS、PVA、CTMAB为分散剂时,粒径均匀且分散性良好,吸波性能皆有提高,尤以PVA为分散剂时吸收性能最佳(14.26 GHz处的最大反射损耗值为-17.33 dB)。     

粉煤灰泡沫陶瓷浆料的稳定机制

通过不同组分浆料的沉降实验,研究了固含量、分散剂（淀粉、硅酸钠、柠檬酸三铵）对浆料稳定性能的影响。实验过程中测量了1#～12#浆料浑浊液和上清液的高度,进而得到浆料的相对沉降高度（RSH）值。通过测量10#、13#、14#浆料在沉降过程中上清液高度的变化,研究了13#、14#浆料的稳定性。实验结果分析发现,在含硅酸钠的悬浮浆料中,随着浆料中固含量的增加,淀粉作为分散剂对浆料的稳定性能的影响减小;在不含硅酸钠的浆料中．这一规律只在3#～6#的浆料中出现;淀粉、柠檬酸三铵作分散剂可显著提高浆料的稳定性。硅酸钠对浆料的分散效果较差,保证素坯在低温强度的状态下,应尽量减少硅酸钠的用量。     

粉煤灰泡沫陶瓷浆料的稳定机制

通过不同组分浆料的沉降实验,研究了固含量、分散剂(淀粉、硅酸钠、柠檬酸三铵)对浆料稳定性能的影响。实验过程中测量了1#～12#浆料浑浊液和上清液的高度,进而得到浆料的相对沉降高度(RSH)值。通过测量10#、13#、14#浆料在沉降过程中上清液高度的变化,研究了13#、14#浆料的稳定性。实验结果分析发现,在含硅酸钠的悬浮浆料中,随着浆料中固含量的增加,淀粉作为分散剂对浆料的稳定性能的影响减小;在不含硅酸钠的浆料中,这一规律只在3#～6#的浆料中出现;淀粉、柠檬酸三铵作分散剂可显著提高浆料的稳定性。硅酸钠对浆料的分散效果较差,保证素坯在低温强度的状态下,应尽量减少硅酸钠的用量。     

Preparation and property of porous hydroxyapatite as an inorganic dispersant used in suspension polymerization

The porous hydroxyapatite (HAP) for suspension polymerization dispersant was prepared using calcium carbonate and phosphoric acid as raw materials. The samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and BET nitrogen adsorption. The results show that the prepared HAP has a porous structure, low particle density, large specific surface area, uniform particle size and does not agglomerate easily between the particles. The preparation conditions for the HAP were optimized as follows: solid content of calcium carbonate aqueous suspension 90 g/L, concentration of phosphoric acid 1.0 mol/L, reaction/aging temperature 50°C, and aging time 3 h. The HAP prepared under optimal preparation conditions has 106.8 m²·g^-1 of specific surface area, which is about 1.5–1.8 times as much as that of Japanese HAP or commercial HAP. Its application result in the suspension polymerization of styrene show that the porous HAP dispersant has high surface activity, excellent suspension dispersibility and stability and can markedly improve the quality of polystyrene beads.     

氧化镧粉体的制备及其对晶粒粒度的影响

以硝酸镧、聚乙二醇和柠檬酸为原料,采用溶胶-凝胶法制备了氧化镧粉体。研究了在制备过程中分散剂种类（聚乙二醇与柠檬酸）、焙烧温度、焙烧时间等因素对氧化镧粉体晶粒尺寸的影响及氧化镧的吸水性能。结果表明：以聚乙二醇为分散剂制备的氧化镧粉体晶粒粒度比柠檬酸为分散剂制备的样品晶粒粒度小;干凝胶在780 ℃下煅烧1 h,可以完全分解为氧化镧。焙烧温度越高,时间越长,晶粒尺寸就越大;氧化镧的吸水性很强,吸水后形成氢氧化镧。该研究可为控制粉体晶粒度提供参考。     

悬浮聚合用HAP／SDBS无机分散体系的作用机理

研究了ＨＡＰ粉末的沉降特性与生成过程，考察了ＨＡＰ粉末和不同表面活性剂配合在苯乙烯单体分散液中的吸附特性，同时研究了ＨＡＰ粉末复合不同表面活性剂的无机分散体系用于苯乙烯单体悬浮聚合时的聚合稳定性。对ＨＡＰ／ＳＤＢＳ无机分散体系用于悬浮聚合时的分散作用机理进行了探讨。简化了用于苯乙烯悬浮聚合用ＨＡＰ的制备方法：取消缓冲体系，缩短陈化时间，室温制备。且制备的分散剂用于聚合时为常量的１／５。     

Al2O3表面化学特性的研究

通过测量粉体在水溶液中的Ｚｅｔａ电位和颗粒大小,探讨了引入不同的分散剂如聚甲基丙烯酸氨（Ｄａｒｖａｎ Ｃ）、聚乙烯亚胺（ＰＥＩ）及 柠檬酸氨（ＤＡＣ）时Ａｌ２Ｏ３粉体表面带电状况及颗粒分散状况的变化。结果表明,在不同分散条件下的水溶液中,Ａｌ２Ｏ３表面的荷电会有非常显著的变化,Ａｌ２Ｏ３粉体的等电点会发生明显的偏移,并且在远离等电点处,Ａｌ２Ｏ３粉体呈单分散状态,在靠近等电点处,Ａｌ２Ｏ３呈现不同     

在无机分散剂存在下苯乙烯悬浮聚合宏观成粒的特征

以苯乙烯悬浮聚合为体系,考察羟基磷酸钙(HAP)或HAP与聚乙烯醇(PVA)复合为分散剂体系时,各种因素如分散剂浓度、油水比、搅拌速度等与瞬时液滴大小及分布之间的关系,并分析讨论瞬时液滴分散、合并的过程特征.结果表明,悬浮苯乙烯液滴聚合宏观成粒的特征与分散剂的分散机理无关,仅体现液滴分散、合并的过程特点.当采用分批加分散剂时,实验观察到瞬时液滴大小分布呈由单峰过渡到双峰,再发展成单峰分布的特征,从而找出了以分批加分散剂方式制备窄分布聚合物颗粒的理论依据.     

Preparation and property of porous hydroxyapatite as an inorganic dispersant used in suspension polymerization

The porous hydroxyapatite (HAP) for suspension polymerization dispersant was prepared using calcium carbonate and phosphoric acid as raw materials. The samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and BET nitrogen adsorption. The results show that the prepared HAP has a porous structure, low particle density, large specific surface area, uniform particle size and does not agglomerate easily between the particles. The preparation conditions for the HAP were optimized as follows: solid content of calcium carbonate aqueous suspension 90 g/L, concentration of phosphoric acid 1.0 mol/L, reaction/aging temperature 50°C, and aging time 3 h. The HAP prepared under optimal preparation conditions has 106.8 m²·g⁻¹ of specific surface area, which is about 1.5–1.8 times asmuch as that of Japanese HAP or commercial HAP. Its application result in the suspension polymerization of styrene show that the porous HAP dispersant has high surface activity, excellent suspension dispersibility and stability and can markedly improve the quality of polystyrene beads. __________ Translated from Journal of Sichuan University (Engineering Science Edition), 2006, 38(6): 73–78 [译自: 四川大学学报(工程科学版)]     

Dispersion of SiC in Aqueous Media with Al2O3 and Y2O3 as Sintering Additives

It has been well accepted that polyethylene imine (PEI) is an effective dispersant for silicon carbide (SiC) in aqueous media. However, after the addition of sintering additives (Al₂O₃ and Y₂O₃), this dispersing effect is reduced significantly. In this work, a second dispersant, citric acid, was used to resolve this problem. It was found that citric acid could decrease the slurry viscosity (without sintering additives) and enhance the PEI adsorption on SiC particle surface. The optimal amount of citric acid required to achieve a minimum viscosity for 55 vol% SiC suspensions was equal to ∼0.87 wt% (at pH ∼6.8). With the aid of citric acid, well-stabilized SiC suspensions (containing sintering additives) were realized, which exhibited slight shear thinning rheologies. After tape casting and SPS sintering, dense SiC samples were obtained with a homogeneous fine-crystalline microstructure. Results showed that citric acid was an effective dispersant for improving the dispersion of SiC particles containing sintering additives.     

激光粒度仪测试阻燃剂级氢氧化镁粒度分布

建立了实用、准确和快速的阻燃剂级氢氧化镁粉体粒度分布的测试方法。采用MS2000激光粒度分析仪研究了待测样品质量、泵转速、分散时间、分散介质、分散剂种类以及分散剂质量浓度等因素对阻燃剂级氢氧化镁粉体粒度分布测试结果的影响。适宜条件:以700 mL水为分散介质,洗洁精为分散剂,分散剂质量浓度控制在0.1~0.3 g/L,氢氧化镁粉体样品质量范围为0.020~0.035 g,泵转速为1 400~2 000 r/min,超声波分散时间为2~5 min,超声波分散后立即测量。     

Effect of citric acid on the synthesis of nano-crystalline yttria stabilized zirconia powders by nitrate–citrate process

The role of citric acid on the preparation of nano-crystalline cubic YSZ powder using a citrate–nitrate solution combustion technique is reported. Thermo-gravimetric analyses reveal that the exothermic peak of nitrate–citrate redox reaction disappears with the increase in citric acid content. The crystallite size of the cubic YSZ powder initially increases with the increase in citric acid content and then decreases upon further addition of citric acid. Particle coarsening has been found to significantly increase upon increase in calcination temperature from 650 °C (11.1 nm) to 800 °C (65.3 nm). Transmission electron microscopic studies in conjunction with XRD analyses indicate a low degree of agglomeration in the synthesized powder. Microwave heating of the solution can control the particle size and yield c-YSZ powder having sizes 15 nm.     

Effects of synthesis conditions on the morphology of hydroxyapatite nanoparticles produced by wet chemical process

Nanoparticles of hydroxyapatite (HAP) were synthesized by means of wet chemical precipitation method, under atmospheric pressure. HAP powders with various morphologies, such as sphere-, rod-, needle-, wire- and bamboo-leaf-like, were obtained by controlling the synthesis conditions. It was found that the solvent systems, dispersant species and drying methods had effects on the particle size and dispersibility. The initial pH values and reaction temperatures both played important roles in the morphology of HAP, as well as the phase formation and degree of crystallinity. The possible influence process of initial pH values and reaction temperatures was discussed in details. The crystal morphology and particle size were analyzed by transmission electron microscopy (TEM) and scanning electron microscope (SEM), and the compositions and chemical structures were identified by X-ray diffractions (XRD) and Fourier transform infrared spectroscopy (FTIR).